The invention relates to an apparatus for marking the operation and/or the position of an induction coil of an inductive cooking field by illumination or illuminated marking. Furthermore, the invention relates to an inductive heating device with such an apparatus.
Induction coils of an inductive cooking field can be located beneath a glass ceramic plate on which is placed a corresponding saucepan. Below this plate is located the induction coil and transmits energy into the bottom of the saucepan for heating purposes.
Such as is e.g. the case with radiant heaters, in many cases it is here desirable to have an optical indication of the operation or position of the heating in the vicinity of the latter. It is possible to place beneath an induction coil illumination means and by means of laterally extracted light guides to mark the induction coil by illumination. However, the electrical connection of the illumination means is complicated. As a result of the location below the induction coil there is an increase in the overall height, which is considered disadvantageous.
The problem of the invention is to provide an apparatus of the aforementioned type and an inductive heating device with which the disadvantages of the prior art are avoided and where in particular an illuminated marking of an induction coil, its operation or its position is possible in a very simple and operationally reliable manner.
This problem is solved by an apparatus having an electric illumination means and a transformatory receiving coil for placing in a magnetic field of an induction coil, the receiving coil being connected to the illumination means, and an inductive heating device. Advantageous and preferred developments of the invention are described in greater detail hereinafter. In the sense of this application the term xe2x80x9ccomprisexe2x80x9d is not to be understood restrictively as xe2x80x9conly comprising the samexe2x80x9d, but instead as xe2x80x9chaving inter aliaxe2x80x9d.
According to the invention said apparatus has a support having or supporting at least one electrical illumination means. The apparatus has a receiving coil, which can be placed in the magnetic field of the induction coil and permits a transformatory energy transmission from the induction coil to the receiving coil. The receiving coil is in turn connected to the illumination means and supplies the latter with energy from the induction coil.
This offers the major advantage that there is no need for electrical connections between an apparatus according to the invention and a power supply, to which is e.g. also connected the induction coil. Thus, there is an energy transmission without direct connection or contact. With a single induction coil several supports or receiving coils around the same can be supplied. In this way an apparatus according to the invention can be manufactured and installed as a relatively autarchic functional and constructional unit. Installation essentially consists of fixing.
In order to consume minimum energy, LEDs are advantageously used as the illumination means. Particular advantage is gained through LEDs, which are heat-resistant up to at least 100xc3x8 C. In this way operation under a glass ceramic cooking field is in most cases easily possible without excess temperature problems. Through the alternative use of glow lamps, excess temperature problems can be completely avoided.
For each receiving coil it is possible to provide several illumination means, the receiving coil advantageously being correspondingly dimensioned in each case. As stated, the illumination means can be LEDs. This has the advantage that they can be connected in oppositely poled manner to the receiving coil in in each case roughly the same number. Thus, in the case of the LEDs both positive and negative phases of the voltage generated in the receiving coil are used.
In a preferred development of the invention the receiving coil is located on the support together with the illumination means. For this purpose the support can be constituted by a printed circuit board. This offers the possibility of constructing the receiving coil in a particularly advantageous manner from the production standpoint through conducting tracks made on the printed circuit board. As high currents do not flow in the receiving coil, said conducting tracks or the turns of the receiving coil can be made very thin and can therefore be relatively closely juxtaposed. Advantageously the receiving coil or its turns can pass or pass round in the outer area of the support, so that in the middle there remains space for the illumination means or further devices. The receiving coil can pass spirally over the support. In order to increase the number of turns per support, the receiving coil can be located on both sides of the support, e.g. in a mutually corresponding manner. These two parts can then be connected.
In the case of a direct connection of the illumination means to the receiving coil, it is possible to obtain the brightness of the illumination means in a manner roughly dependent on the power of the induction coil. This provides additional information on the operating state of the induction coil.
According to another development of the invention a substantially power-independent lighting or illumination can be obtained by providing voltage limiting means for the illumination means. To minimize brightness fluctuations, upstream of the LEDs can be connected series resistors. They are preferably placed on the same support as the illumination means in each case connected thereto. In particularly preferred manner they are located close to the illumination means.
For the case that in conventional manner an induction coil has a flat, circular construction, the support can have an essentially circular ring sector shape. This means that one or more supports together can surround the induction coil. According to one possibility such a circular ring sector can extend over an angular range of approximately 120xc3x8. Thus, with three such supports it is possible to border the induction coil. The radius of a support with circular ring sector shape can be chosen in such a way that the support is in accordance with the induction coil shape and has a specific spacing therefrom. This spacing can be a few millimeters to a few centimeters, e.g. 10 to 20 mm. Here spacing is understood to mean the spacing between the induction coil and the receiving coil.
It is possible by lighting means to mark an induction coil, which as a rule gives a roughly punctiform illumination. According to a further development of the invention light distribution means can be associated with the at least one illumination means and by means thereof it is possible to bring about a larger or elongated or even areally distributed light phenomenon. Such light distributing means are known from other fields of application, e.g. as lighting tracks. The light distributing means can be placed over one or more illumination means. They are preferably made from a transparent plastic. Their path generally corresponds to the desired path of a lighting means. Their path in particular roughly corresponds to the shape of an induction coil and e.g. forms an illuminating circular ring surrounding the same.
In order to avoid thermal problems, above the apparatus can be provided a thermal insulation, which is translucent at least in the vicinity of the illumination means. Such an insulation can e.g. be connected to the support by means of a holder or spacer, so as to form a constructional unit. From the surface the insulation at least covers and better still projects over the top of the apparatus. It is in this way possible in the case of particularly strongly heated saucepan bottoms, which have become laterally displaced and are located above the apparatus or illumination means, to prevent overheating of the illumination means or the apparatus or the receiving coil. Thus, the thermal insulation is intended to shield the apparatus up to the cover or cooking field. The insulation can e.g. be glass or a heat-resistant plastic, which should be provided with a corresponding coating. For this purpose are particularly suitable IR-reflecting coatings.
In particularly advantageous manner an apparatus according to the invention is independent of the construction of an induction coil. It is possible in this way to construct an apparatus for the retrofitting of a random induction coil or random induction cooking point.
In addition, the aforementioned set problem is advantageously solved by an inductive heating device. With such an inventive, inductive heating device, which can in particular be an induction cooking field, close to the induction coil is provided at least one of the aforementioned devices or supports.
In a preferred development of the invention an induction coil is substantially surrounded by illumination means on one or more supports. It is advantageous if the illumination means have a substantially identical lateral spacing, e.g. a few centimeters, with respect to the induction coil. For marking and in particular accentuating the circular shape of the induction coil there should be at least four and advantageously far more illumination means. Thus, a punctiform or, by means of the aforementioned light distributing means, a strip-like lighting image can be created around the induction coil.
If the supports of the apparatuses are circular ring sectors, e.g. ⅓ circular ring sectors, a fitting thereof is easily possible. This can e.g. be such that the induction coil, particularly with several induction coils together, is secured to a base holder and at least one support is fixed to the latter. Fixing can e.g. take place by adhesion, particularly using two-sided foam adhesive strips.